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Why the same function is taking more time after MEX creation?

Asked by JAI PRAKASH on 27 Aug 2018
Latest activity Edited by Ryan Livingston on 29 Aug 2018
I want to create mex of 'sort()' funtion.
So I build below function
function idx = sort2(h) % h is 600x1280 'single' elements
[~,idx] = sort(h(:)); % because I just want indices only, I dont want the elements.
end
If I call above funtion:
Why the 'MEX' is taking more time??

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R2018a

1 Answer

Answer by Ryan Livingston on 28 Aug 2018
Edited by Ryan Livingston on 29 Aug 2018
 Accepted Answer

The MATLAB Coder documentation has a section covering acclerating MATLAB code via MEX generation:
One page that's relevant to what you are seeing is:
It contains the statement:
Use MEX functions to accelerate MATLAB code only if user-generated code dominates the run time.
Avoid generating MEX functions if computationally intensive, built-in MATLAB functions dominate the run time. These functions are pre-compiled and optimized, so the MATLAB code is not accelerated significantly using a MEX function.
In MATLAB, sort is a built-in function that is hand-optimized and compiled. So the generated code likely won't be any faster and can be slower in some cases.

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good information
Thanks @Ryan

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